1. Field of the Invention
The present invention relates to apparatus and methods for manufacturing fiber bundles, in particular hollow fiber membrane bundles, in particular for the manufacture of dialysis filters.
2. Description of the Prior Art
The main field of use of such fiber bundles is the manufacture of dialysis filters, i.e. of filters for extracorporeal blood treatment processes, for example for hemodialysis, hemofiltration and hemodiafiltration. In accordance with the prior art, fibers for such filters are manufactured by continuously operating hollow fiber spinning machines. The hollow fibers continuously exiting the hollow fiber spinning machine are usually wound batch-wise e.g. onto slowly rotating reel wheels. The reel wheels have winding mandrels distributed uniformly over the periphery and the hollow fibers lie on them. The hollow fibers are thereby freely tensioned between the winding mandrels. The spacings between the winding mandrels are selected such that one or two hollow fiber bundles arise between two respective winding mandrels. These hollow fiber bundles are wrapped with a thin plastic wrapping film by hand and fixed manually. As soon as the hollow fiber bundle has been fixed in this manner, it is cut off at the desired length by hand again using a cutting apparatus. Finally, the hollow fiber bundle is introduced into a cylindrical filter cartridge and the wrapping film of plastic is removed again. Manufacturing methods of this type are known, for example, from U.S. Pat. No. 4,276,687.
The manufacture of a long fiber bundle which is cut into a plurality of individual bundles after the reeling and wrapping is known from JP 10-194606 A. In this process, the membrane fiber is wound up onto a receiving wheel or reel wheel whose circumference corresponds to a multiple of the length of a finished hollow fiber bundle. As soon as the desired number of hollow fibers has been wound up, the complete hollow fiber strand is cut through at one point and pulled off the receiving wheel or reel wheel so that a linear hollow fiber strand is present which is now wrapped in a spiral form by a fixing tape and then cut to the desired length of the individual bundles. To realize a quasi continuous operation, two fixed receiving wheels are operated in parallel. The alternating transfer of the hollow fibers to the one or the other receiving wheel takes place by a movable hollow fiber feed. This method, however, has the disadvantage that pulling forces have to be exerted on the hollow fiber strand and frictional relative movements occur between the outer hollow fibers of the hollow fiber strand the guide elements of the machine. In addition, during the winding off, the position of the individual hollow fibers within a hollow fiber bundles necessarily also changes because the circumference of the individual wrapping increases in the radial direction during winding up. In addition, the spiral wrapping with a fixing tape is technically extremely complex and results in a low efficiency of the method.
A method for the wrapping of a fiber bundle is known from DE 198 06 293 A1 in which the fiber bundle is placed on a film into a bent over steel metal sheet which is thereupon allowed to spring back into its relaxed position in which it forms a cylinder and thus wraps the film around the fiber bundle. In this connection, however, the force exerted on the fiber bundle can only be controlled with difficulty since it substantially depends on the restoring force of the steel metal sheet so that the precision of the fiber bundles produced suffers.